Journal of Electroceramics最新文献

In this study, micro-tubular solid oxide fuel cells (MT–SOFCs) were manufactured by successive electrophoretic deposition (EPD) in non-aqueous solvent. At first, stable suspensions of YSZ (Electrolyte), Ni/YSZ (anode) and LSM (cathode) in isopropanol were prepared. The EPD was performed on graphite rods under various voltages and times. The proper EPD condition was determined to prepare porous electrodes and dense electrolyte layers. The graphite rod was decomposed by heating at 900˚C and the resulting tubular thin films were sintered in air at 1350˚C. The microstructure of the sintered samples was studied by SEM analysis. The performance of the SOFC was investigated by electrochemical impedance spectroscopy. It was found that MT–SOFC with an internal diameter of 0.7 mm can be obtained via successive EPD. The maximum power density of the cell was 0.25 W/cm²at 850˚C.

X-ray diffraction (XRD) is an indispensable tool for characterising thin films of electroceramic materials. For the beginner, however, it can be a daunting technique at first due to the number of operation modes and measurements types, as well as the interpretation of the resultant patterns and scans. In this tutorial article, we provide a foundation for the thin-film engineer/scientist conducting their first measurements using XRD. We give a brief introduction of the principle of diffraction and description of the instrument, detailing the relevant operation modes. Next, we introduce five types of measurements essential for thin film characterisation: (2theta /omega) scans, grazing-incidence scans, rocking curves, pole figures, and azimuth scans (or ϕ scans). Practical guidelines for selecting the appropriate optics, mounting and aligning the sample, and selecting scan conditions are given. Finally, we discuss some of the basics of data analysis, and give recommendations on the presentation of data. The aim of this article is to ultimately lower the barrier for researchers to perform meaningful XRD analysis, and, building on this foundation, find the existing literature more accessible, enabling more advanced XRD investigations.

0.675BiFeO₃-0.3BaTiO₃-0.025LaFeO₃-x mol% Nb₂O₅ (x = 0–1.25) multiferroic lead- free ceramics, fabricated by conventional solid-state reaction, were studied to reveal the effects of Nb₂O₅ on the structural, morphology, dielectric, ferroelectric, magnetic and magnetoelectric properties of the BiFeO₃-based ceramics. After the addition of Nb₂O₅, the crystal structure of as-prepared samples remained orthorhombic phase. The doping Nb⁵⁺ ion could be able to inhibit grain growth remarkably and suppress the creation of oxygen vacancies of this ceramics, which resulted in the improvement of electrical insulation by two orders of magnitude. The ferromagnetism was apparently enhanced with increasing content of Nb₂O₅, and the observed remanent magnetization Mr peaked at 0.022 emu/g for x = 1. Suitable amount of Nb₂O₅ could be beneficial to the dielectric properties, with the optimal x at 0.75, with dielectric constant ε_r of 918 at 100 Hz. The observed magnetoelectric coefficient α_ME suggested the existence of magnetoelectric coupling effect in these ceramics. The α_ME value almost decreased after adding Nb₂O₅, possibly due to the obvious degradation of ferroelectric behaviors.

The effect of crystallographic structure and texture on the fracture behavior of lead zirconate titanate (PZT) ceramics was investigated. PZT ceramics with Zr/Ti ratio of 45/55 (tetragonal, T), 52/48 (morphotropic phase boundary, MPB), and 60/40 (rhombohedral, R) were fabricated, and then textured using electric field and/or mechanical stress. Vickers indentation method was employed to characterize their fracture behavior. Results show that the unpoled specimen exhibits fracture toughness isotropy, with values of 1.24 MPa·m^1/2, 1.07 MPa·m^1/2, 1.17 MPa·m^1/2 for T, MPB, and R, respectively. The textured specimen reveals fracture toughness anisotropy (FTA). The largest FTA was observed for the mechanically (M) poled specimens. Additionally, FTA for the MPB composition was larger than the T and R specimens. The crystallographic structure and texture dependent domain switching behavior, and the parameters of coercive stress and Young’s modulus measured by mechanical compression are used to explain the observed phenomena.

The work is devoted to the study of the mechanical properties of porous ceramics based on diatomite, which has high porosity, adsorption capacity, weak thermal and acoustic conductivity, refractoriness and acid resistance. Based on the morphological analysis of the samples, the numerical value of the sample’s porosity was determined. The mechanical properties of the samples were determined by static and dynamic loading methods. The values of static and dynamic elastic moduli of the samples were experimentally measured. The research results showed that, for the material under consideration, at the initial stages of compression processes, the processes of elastic deformation are mainly realized with the subsequent transition to the region of plastic deformation. It was also found that for highly porous samples in the elastic deformation region, the manifestation of pressing processes is possible. In this work, the study of the dependence of the dynamic modulus of porous diatomite ceramics on porosity was carried out: a decrease in elastic moduli was recorded with an increase in the material porosity. A decrease in material porosity after deformation is found.

Abstract

The 0.93(Bi_0.5Na_0.5)TiO₃-0.07BaTiO₃ doped with different amount of (Ga_0.5Ta_0.5)⁴⁺ complex-ion from 0 to 4 mol% (abbreviated as BNBT-100xGT) ceramics were prepared. Phase analysis revealed that up to x = 0.035, Ga³⁺ and Ta⁵⁺ completely dissolve in BNBT perovskite structure and substitute in B-site. Increase in x more than 0.02 resulted in formation of pinched P-E loops accompanied by sharp decrease in P_r. This observation can be attributed to the phase transition from ferroelectric (FE) to a non-polar ergodic relaxor (ER) which could be transformed reversibly to a FE phase by applying an electric field. According to temperature-dependence dielectric constant results, transition temperature from FE to ER phase decreased and for ceramic with x = 0.03 shifted to lower than room temperature with increasing GT content. As a result, enhanced unipolar electric field-induced strain (0.4% under 60 kV/cm) corresponding to d₃₃^* of 667 pm/V was obtained in this ceramic. The large electrostrain is accompanied with relatively large hysteresis, which should be lowered for actuator applications. However (Ga_0.5Ta_0.5)⁴⁺ complex-ion doping of BNT-based ceramics, could be considered as an efficient approach to enhance electrical properties, especially electrostrain characteristic of these ceramics, as competitive alternatives to lead-based ceramics.

y mol% Fe-doped Ba(Zr_0.2Ti_0.8)O₃—x mol%(Ba_0.7Ca_0.3)TiO₃ (abbreviated as yFe:BCZTx) ferroelectric ceramics with y = 0, 0.375, 0.75, and 1.5 across the morphotropic phase boundary (MPB) with x = 44 and 56 were fabricated via conventional solid state reaction methods. Fe incorporated into the lattice and all the yFe:BCZTx ceramics showed pure perovskite structure. Fe-doping can significantly reduce the grain sizes and shift the tetragonal-cubic phase boundary toward lower temperature for all the investigated compositions across the MPB. A moderate enhancement of frequency dispersion on the dielectric constant was observed. The temperature dependent dielectric constant was analyzed according to modified Curie–Weiss law and the diffuse factor increased with increasing Fe-doping content. Relaxor-like slim polarization–electric field (P-E) loops were obtained for all BCZTx ceramics after Fe-doping. 1.5Fe:BCZTx ceramics shows almost hysteresis free P-E loops without obvious fatigue behavior after 10,000 cycles. The recoverable energy storage efficiency was significantly enhanced in 1.5Fe:BCZTx ceramics with good temperature stability. Our results indicate Fe-doping can be used as a universal phase boundary shifter and to increase energy storage efficiency for BCZT ceramics.

The fluctuating force from the dynamic system applied to the piezoelectric material gives electric energy as an output. In the present work, the effect of pressurizing the diaphragm type piezoelectric elements at the same time and at a different time (depicting the condition of in-phase and out-of-phase) has been studied. Furthermore, to combine the outputs, the use of series and parallel circuitry has been studied before the rectification (AC to DC) and after the rectification. The material of the piezoelectric used in the experiments was lead zirconate titanate (PZT). The maximum power output of 362.8 µW is obtained when the two piezoelectric elements were pressurized in-phase by a cyclic force of amplitude 400 mA and 17 Hz frequency, their signals rectified and then combined through the parallel circuit. The high power output is at the natural frequency of the mechanical system.

The luminescent properties of Pr³⁺ ion-doped t-type LaVO₄ phosphor synthesized by the hydrothermal method were investigated. The XRD results shows that the optimum conditions for preparing t-type LaVO₄ are 180 ^oC, 16 h. These particles are homogeneous distribution with uniform particle sizes for various Pr³⁺ ion concentrations, but the particle sizes seem to be increased with increasing Pr³⁺ ion contents. For Pr³⁺ ion-doped m-type and t-type LaVO₄ phosphor, the absorption and excitation behavior are almost the same, but there is an obviously difference for emission behavior. The main emission peak is from the ¹D₂→³H₄ transition for Pr³⁺ ion-doped t-type LaVO₄ phosphor. The Commission International de I’Edairage chromaticity coordinates shifted from blue region to white region, and then shift to light-blue region. A single white light emitting phosphor can be obtained if the Pr³⁺ ion concentration is appropriate.